Pulmonary aspiration is a serious medical problem. Pulmonary aspiration is defined as misdirection of oropharyngeal secretions or gastric contents into the larynx and/or the lower respiratory tract. Pulmonary aspiration may be the cause of various syndromes, but the most important include aspiration pneumonitis (caused by aspiration of gastric content) and aspiration pneumonia (caused by aspiration of oropharyngeal secretions colonized by bacteria). [Marik, Paul Ellis. Handbook of Evidence based Critical Care. New York: Springer, 2010; Marik, Paul E. “Pulmonary Aspiration Syndrome.” Current Opinion in Pulmonary Medicine 17 (2011): 148-54.]
Pulmonary aspiration of gastric contents is a recognized and feared complication of general anesthesia. Pulmonary aspiration also frequently occurs in trauma or ICU patients with altered states of consciousness, such as head trauma, alcohol or drug-induced states and cerebrovascular accidents. [Crit Care Med. 2011 April; 39(4): 818-826.] If a patient is sedated, unconscious or otherwise disabled, gastric contents are more likely to be aspirated. Aspiration may result from obstruction of the pharynx, weakness or incoordination of the pharyngeal muscles, poor opening of the upper esophageal sphincter, or other impairments. [Mizuko, Mark. “Aspiration.” Aspiration. University of Minnesota Duluth, Web. 10 Jul. 2013.] Administration of sedation can produce an unconscious patient at risk for developing emesis with pulmonary aspiration. During conscious sedation, procedural physicians may attempt to avoid this problem by administering sedatives sparingly, which, though reducing the risk of the complication, may also increase the chance that the patient does not receive adequate relief from pain outside the practice of anesthesiology. [http://www.ncbi.nlm.nih.gov/pubmed/1501047; http://felipeairway.sites.medinfo.ufl.edu/files/2009/11/sga-and-aspiration.pdf]
A relatively small amount of aspirate can cause significant problems or even death. The critical volume of aspirate sufficient to cause aspiration pneumonitis is often stated as 25 ml with a pH<2.5; this is derived from unpublished work on Rhesus monkeys, extrapolated to humans. [Engelhardt, T. and N. R. Webster. “Pulmonary Aspiration of Gastric Contents in Anaesthesia.” British journal of Anaesthesie 83.3 (1999): 453-60.]
Each year many deaths occur in hospitals and nursing homes due to pulmonary aspiration. This is due both to the inability of patients to call for help (due to unrelated medical issues, coma, dementia, etc.) upon an aspiration event and the failure of nursing staff, using current monitoring practices, to detect many instances of pulmonary aspiration within a sufficient amount of time.
Currently, initial recognition of aspiration is possible by way of visible gastric contents in the oropharynx, or more subtle indications such as hypoxia, increased inspiratory pressure, cyanosis, tachycardia or abnormal auscultation. [King, Wendy. “Pulmonary Aspiration of Gastric Contents.” Update in Anaesthesia 3 (2011): 28-31.] Long term symptoms of aspiration are bluish discoloration of the skin caused by lack of oxygen, chest pain, coughing up foul-smelling, greenish or dark phlegm (sputum) or phlegm that has pus or blood, fatigue, fever, shortness of breath, wheezing, breath odor, excessive sweating and/or problems swallowing. [“Health Guide.” Aspiration Pneumonia. The New York Times Company, 24 Jan. 2013. Web. 10 Jul. 2013.]
A few patents have addressed emesis events. An aviator's breathing mask device that gives complete protection from external atmosphere while providing for disposal of effluent into an effluent receiver has been provided by Vicenzi in U.S. Pat. No. 4,537,189, which includes a one way valve leading to an expandable flexible bag for containing effluents. A face mask for police detainees with a central folded region open at the lower edge to receive effluents to prevent pooling of vomit within the mask is provided by Collins in U.S. Pat. No. 6,971,389. But none of these patents provide a system that will detect and notify medical personnel of an episode of aspiration.
Accordingly, there is a need for a system to assist in removing aspirate and to rapidly detect emesis and/or aspiration to allow a rapid response to the situation by attending medical staff.